- EPS Electronic Power Shift rear derailleur. This rear derailleur requires specific, separate EPS interface and power unit, battery pack, and shifters- External carbon outer plate surrounds the technopolymer, carbon fiber upper and lower body and molded carbon cage- The optimized, oversized parallelogram operates with absolute precision- Activation is achieved through a main screw mechanism and a specially designed high torque motorized gear box- All EPS rear derailleurs feature an exclusive unlock, back home system that prevents damage in case of a crash